1. Field of the Invention
This invention relates to stereoscopic viewing systems, and more particularly to a projection system in which the need of a viewing hood, polaroid glasses, prisms or other viewing aids is completely eliminated.
2. Description of the Prior Art
Various stereo projection methods or systems have been employed in the past to provide optical displays of or permit viewing of an image in three dimensions. One type of system, known as "diffuse stereo screen projection," projects the image onto a diffuse screen and provides the advantage that viewing is not limited to a precise number of viewers. A plurality of viewers or spectators may fit into the room housing the diffuse stereo projection screen, however, the disadvantages of this method are numerous. The system is characterized, in a typical film projection system, by the requirement of projecting onto the screen images through a lens system from left and right films through the use of left and right polairzers respectively and requiring in turn viewing of the projected image through polarized glasses whose lenses are polarized corresponding to those of the right and left polarizer of the optical projection system. Further, a lenticular screen must be used to preserve the polarization of the projected images. This method has poor power efficiency due to the wide viewing field of the screen, and consequently intense transparency illumination is necessary for proper projection. Another system utilizes a split field created by a set of prisms or mirrors. The viewer must view the scene by looking into a hood or wear a special set of prism glasses, both restricting his view of other data in the vicinity of the screen.
Attempts have been made to achieve direct viewing of a stereo image by a number of people, in several ways. One arrangement employs stereo viewing consoles at specific stations in which the screen displaying the stereo image at each location receives that image by way of a beam splitter such that the projected image is split into multiple beams after initial projection from the stereo projector. While the beam splitters may be installed or removed to variably accommodate the number of viewers, each additional viewer requires a beam splitter and the intensity of the lamp to maintain the brilliance of the multiple images being viewed, must be increased accordingly. In such systems, there is a limit to the intensity of the source without damaging the transparencies or photographic prints.